The present invention relates to sealing rings to be set between the engine block of an internal-combustion engine and a cylinder head fixed to said engine block, in which each ring is received in a seat formed around a cylinder within at least one of the mutually facing surfaces of the engine block and of the cylinder head, and in which said sealing ring comprises a hollow annular body, constituted by an elastically deformable material, provided within which is a shape-memory material.
A sealing ring of the type specified above is, for example, described and illustrated in the document No. WO-A-2005 119102, filed in the name of the present applicant.